Atropine

證據等級: L5

預測適應症: 10 個

Atropine: From Bradycardia and Organophosphate Poisoning to Migraine Disorder

One-Sentence Summary

Atropine is a classical anticholinergic drug used in clinical practice for symptomatic bradycardia, as an antidote for organophosphate poisoning, and as a preanesthetic agent to reduce secretions. The TxGNN model predicts it may be effective for migraine disorder by blocking the parasympathetic signalling that drives neurogenic inflammation during migraine attacks, with no registered clinical trials and 13 publications — all indirect mechanistic or animal studies — currently supporting this direction. Importantly, a related headache prediction (post-dural puncture headache, PDPH) carries Phase 3 trial support for the Neostigmine+Atropine combination, representing the most immediately actionable finding in this report.

Quick Overview

Item	Content
Original Indication	Symptomatic bradycardia; organophosphate poisoning antidote; preanesthetic antisecretory use
Predicted New Indication	Migraine Disorder
TxGNN Prediction Score	99.56%
Evidence Level	L4
South Africa Market Status	Not marketed
Number of SAHPRA Registrations	0
Recommended Decision	Hold

Why is This Prediction Reasonable?

Detailed mechanism of action data for Atropine is not available in the current dataset. Based on well-established pharmacology, Atropine is a competitive, non-selective antagonist of muscarinic acetylcholine receptors (mAChR, M1–M5 subtypes). By blocking the effects of acetylcholine at parasympathetic neuroeffector junctions and in the central nervous system, Atropine produces tachycardia, reduced glandular secretions, bronchodilation, mydriasis, and — at higher doses — central anticholinergic effects including cognitive changes.

The predicted link to migraine centres on the role of the parasympathetic nervous system in migraine pathophysiology. The sphenopalatine ganglion (SPG) — the largest cranial parasympathetic relay centre — when activated, drives neurogenic inflammation of the dura mater, the membrane lining the brain. This process involves dural vasodilation, plasma protein extravasation, and release of neuropeptides such as calcitonin gene-related peptide (CGRP), all of which contribute to the migraine pain cascade. A 2024 experimental study (PMID 36485173) confirmed that cholinergic modulation via meningeal mast cells — including with muscarinic antagonists — influences this neuroinflammatory process in a rat nitroglycerin-induced migraine model. A 1997 animal study (PMID 9344563) further demonstrated that direct electrical stimulation of the SPG induces dural plasma protein extravasation, establishing the SPG as a druggable parasympathetic target in migraine.

Despite this plausible mechanistic basis, all available evidence remains indirect. Atropine appears in the migraine literature as a pharmacological tool — used to confirm cholinergic pathway involvement in vasomotor responses and antinociception — rather than as the investigational treatment itself. A 1986 clinical observation (PMID 2943405) noted that systemic atropine markedly reduced autonomic attack features (sweating, tearing, nasal secretion) in four patients with chronic paroxysmal hemicrania, providing the single direct clinical signal that mAChR blockade can modify a headache syndrome. No prospective clinical trial has evaluated Atropine as a migraine therapy, and the appropriate dose, route of administration, and target patient population remain entirely undefined.

Clinical Trial Evidence

Currently no clinical trials directly evaluating Atropine for migraine disorder have been registered on ClinicalTrials.gov or ICTRP.

Note on Related Headache Evidence: For the post-dural puncture headache (PDPH) indication (TxGNN Rank 8, Evidence Level L2), three Grade A clinical trials directly evaluating the Neostigmine+Atropine combination have been identified — see the Conclusion and Next Steps section below.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
36485173	2024	Mechanistic lab study	European Journal of Neuroscience	Investigated cholinergic modulation via meningeal mast cells in a rat nitroglycerin-induced migraine model; muscarinic blockade reduces mast-cell-driven neurogenic inflammation — the most directly relevant study to the mAChR-migraine hypothesis
9344563	1997	Animal study	Experimental Neurology	SPG parasympathetic stimulation induces dural plasma protein extravasation in rats; atropine-sensitive cholinergic signalling underlies this SPG-mediated neurogenic inflammatory response
8930196	1996	Animal study	J Pharmacology & Experimental Therapeutics	Central atropine injection blocked sumatriptan antinociception in rodents and guinea pigs; demonstrates that central muscarinic pathways contribute to antimigraine drug efficacy
2943405	1986	Clinical observation	Cephalalgia	Systemic atropine markedly reduced autonomic attack features (sweating, tearing, nasal secretion) in 4 patients with chronic paroxysmal hemicrania — the only direct clinical observation of mAChR blockade modifying a headache syndrome
10193781	1999	Animal pharmacology	British Journal of Pharmacology	Atropine (3 µM) used as pharmacological probe in basilar artery relaxation studies; nicotine-evoked relaxation partially atropine-sensitive — relevant to migraine-associated vasomotor pharmacology
15882801	2005	Animal study	Neuroscience Letters	Cholinergic-nicotinic pathways shown to contribute to CGRP release and facial blood flow changes in a centrally evoked trigeminovascular model relevant to migraine triggers
17186568	2007	Review	Journal of Applied Toxicology	Pharmacological review of anisodamine (an atropine derivative); outlines mAChR antagonist class effects including CNS and vascular actions relevant to the migraine mechanistic hypothesis
1786517	1991	Pharmacological experiment	British Journal of Pharmacology	Ergotamine and DHE pharmacology at 5-HT1C receptors in piglet choroid plexus; contextual background pharmacology of classical antimigraine agents

South Africa Market Information

Atropine (DrugBank ID: DB00572) is not currently registered with SAHPRA and holds no approved product licences in South Africa based on the data available for this report. There are no SAHPRA-registered products to list.

Healthcare professionals in South Africa requiring atropine for established indications (e.g., bradycardia, organophosphate antidote, perioperative use) should contact SAHPRA regarding the section 21 unregistered medicine authorisation process, and consult the current SAHPRA register for any updated product registration status.

Safety Considerations

Please refer to the SAHPRA-approved Professional Information (PI) for safety information. Report adverse drug reactions to SAHPRA.

Pharmacological safety signals identified from the literature:

Intraocular pressure (IOP) elevation — contraindication signal: Atropine’s mydriatic and cycloplegic effects reduce aqueous outflow, raising IOP. Clinical studies from 1968 (PMID 5640848, long-term anticholinergic use in open-angle glaucoma patients) and 2025 (PMID 40932733, cohort study of children on topical atropine for myopia control) document this effect. Atropine is contraindicated in patients with open-angle or angle-closure glaucoma, and IOP screening must be included in any headache trial protocol.
Cardiovascular effects: Tachycardia, palpitations, and arrhythmias are expected pharmacodynamic effects. Use with caution in patients with pre-existing ischaemic heart disease or arrhythmias.
RCVS safety signal with Neostigmine+Atropine: A 2023 case report (PMID 37802666, British Journal of Anaesthesia) documented reversible cerebral vasoconstriction syndrome (RCVS) following Neostigmine+Atropine administration for PDPH — a rare but serious neurological adverse event. Neurological monitoring is warranted when this combination is used.

Conclusion and Next Steps

Decision: Hold

Rationale: The TxGNN prediction for migraine disorder is mechanistically plausible — Atropine’s mAChR blockade could theoretically attenuate SPG-driven neurogenic inflammation — but is supported only by indirect preclinical and mechanistic evidence (Evidence Level L4). No clinical trial has directly tested Atropine for migraine, the drug is not currently registered with SAHPRA, and critical data including the MOA dataset, safety PI, and dose-route definition for neurological use are all absent.

To proceed, the following is needed:

MOA documentation: Retrieve complete mechanism of action data from DrugBank to strengthen mechanistic analyses and support any regulatory submission
SAHPRA registration pathway: Assess section 21 authorisation or formal registration requirements for established atropine indications in South Africa before initiating any new indication programme
Proof-of-concept trial design: A small, controlled study evaluating selective mAChR antagonism on SPG-mediated outcomes in migraine patients would be needed to advance evidence from L4 to L2 or L3
IOP pre-screening requirement: Any clinical protocol must include baseline and periodic intraocular pressure assessment, with exclusion of patients at risk of glaucoma
Glaucoma and PDPH contraindication review: Given the IOP-elevation pharmacological signal, open-angle glaucoma (Rank 5) and primary hereditary glaucoma (Rank 6) should be flagged as contraindicated indications rather than repurposing candidates

Priority Finding — Post-Dural Puncture Headache (Rank 8, Evidence Level L2): Proceed with Guardrails

The strongest clinical evidence in this entire Evidence Pack relates not to the top TxGNN prediction, but to the Neostigmine+Atropine combination for PDPH (TxGNN Rank 8). The key evidence includes:

Trial	Phase	Status	n	Relevance
NCT04910477	Phase 3	Completed	90	Direct comparison of nebulised Neostigmine+Atropine vs Dexmedetomidine for PDPH after caesarean section; highest-grade direct trial evidence
NCT03997006	Phase 4	Completed	60	Head-to-head RCT: IV Neostigmine+Atropine vs IV Aminophylline for PDPH treatment
NCT06729047	Phase 1/2	Not yet recruiting	330	Large prophylactic trial: IV Neostigmine+Atropine vs Ketorolac for PDPH prevention
NCT03587441	Phase 4	Completed	240	Neostigmine intrathecal adjuvant to reduce PDPH incidence; Atropine as required co-agent

PMID	Year	Type	Key Finding
30169405	2018	RCT	Landmark trial (Anesthesia & Analgesia): Neostigmine+Atropine added to conventional PDPH management significantly reduced headache severity
36651373	2023	RCT	Confirms Neostigmine+Atropine efficacy vs nebulised dexmedetomidine for PDPH after caesarean section
37802666	2023	Case report	RCVS reported after Neostigmine+Atropine for PDPH — critical safety signal requiring neurological monitoring

Clinical context: In PDPH, Atropine functions as a safety co-agent — its role is to counteract neostigmine’s peripheral mAChR side effects (bradycardia, hypersalivation, intestinal hypermotility), enabling safe neostigmine delivery. Atropine is not an independent PDPH treatment. A dedicated evidence pack focused on the Neostigmine+Atropine combination for PDPH is recommended for full regulatory and clinical evaluation.

Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.